1. Field of The Invention
This invention pertains to the art of reclosable plastic bags having extruded zippers, and more particularly to fastener profiles which interlock with one another to seal such bags. More specifically, one of the two fastener profiles on either side of the bag opening has a spreader, which may be wedge-shaped, and which fits into a space between interlocking members on the other of the two fastener profiles to spread them apart relative to one another, so that they may be more firmly interlocked with those on the other fastener profile when the bag is sealed.
2. Description of the Prior Art
Reclosable bags used, for example, for storing household foodstuffs are typically made of polyethylene. As shown in U.S. Pat. No. 3,416,199 to Imamura commonly assigned with the present invention, a reclosable bag may be formed of two opposed walls equipped at the mouth with fastener profiles. These profiles may include a male profile attached to one wall and a female profile attached to the other wall, or interlocking rib and groove members on the two walls, or interlocking hooks on the two walls. In all of these possible forms, the profiles are shaped so that, when they are aligned and pressed together into an engaging relationship, they form a continuous closure for the bag. The bag may be opened by pulling the walls apart thereby separating the profiles. Various geometric shapes and arrangements for such profiles are shown in U.S. Pat. Nos. Re. 28,969; 3,323,707; 4,212,337; 4,363,345; 4,561,108; and 4,812,056, as well as in U.S. Pat. Nos. 2,558,367; 2,780,261; 2,606,351 and 3,054,434. In addition, U.S. Pat. Nos. 4,736,496 and 5,012,561 disclose reclosable bags with profiles and internal ribs adjacent to the profiles. U.S. Pat. No. 4,822,539 discloses a reclosable bag with interlocking profiles, internal guiding ribs disposed adjacent to the profiles, and stabilizing beams disposed on the outside surface of the bag wall. U.S. Pat. No. 3,338,285 discloses a reclosable bag having several parallel interlocking male and female profiles. In general, the profiles must be such as to provide relatively high resistance to opening from inside the bag while rendering the bag relatively easy to open from the outside.
Other relevant patents are U.S. Pat. Nos. 3,038,225; 3,372,442; and 3,410,327 The first of these, U.S. Pat. No. 3,038,225, shows a separable fastener which includes a wedge-shaped projection. U.S. Pat. No. 3,410,327 shows a profile which is easier to open from the outside than from the inside.
Finally, U.S. Pat. No. 5,140,727 shows a zipper for a reclosable plastic bag wherein a part of at least one of the interlockable rib and groove profiles is structurally discontinuous along its length and substantially free of interdigitation with the opposing profile when interlocked therewith. The structural discontinuities impart a vibratory or bumpy feel perceptible to the touch or an audible clicking sound continually therealong when the profiles are interlocked or separated from each other.